Gargantuan, venom-filled Portuguese man o' war — jellyfish "with tentacles as long as five London buses" — are invading the English coastline, sounding alarm bells for scientists, swimmers and surfers, The Daily Mail reports.

Usually found in the depths of the Pacific and around Australia, the sea creatures, which can grow to 160 feet, have begun drifting along the English coastal areas of Devon and Cornwall, according to Reuters.

A national jellyfish survey suggests marked increases in the number of jellyfish species in the United Kingdom, according to Peter Richardson of the MCS Biodiversity and Fisheries.

More than 1,000 reports involving hundreds of thousands of jellyfish were received in 2013, a record year, and in 2014 the number of reports grew to 1,400, Richardson said. Through July 2015, the survey had already received 1,000 reports.

With August a peak month for jellyfish sightings, 2015 is expected to set another record, he added.

'The million-dollar question is why is this happening? At the moment we just don't know," Richardson said.

Barrel jellyfish sightings typically comprise 10 percent of yearly reports made to Richardson's organization, but in 2014 they accounted for 40 percent of the reports, and so far this year they make up 75 percent, he said.

The jellyfish's venom can travel to the lymph nodes, which can be fatal. Those at greatest risk of dying from stings are the very young, the elderly and those with frail immune systems.

"The creature's venomous tentacles can deliver a painful sting, similar to a cut with a knife, with rash-like symptoms developing immediately," according to Reuters.

"However, the pain depends on the level of exposure."

The area should be immediately rinsed with warm water or sea water and the stingers carefully removed, according to the Daily Mail, which notes that British doctors are advising anyone stung by a jellyfish to seek immediate medical attention.
Related Stories:

Gargantuan, venom-filled Portuguese man o' war - jellyfish with tentacles as long as five London buses - are invading the English coastline, sounding alarm bells for scientists, swimmers and surfers, The Daily Mail reports.